Could be that they don't want to stress the power assembly too much. I imagine most would want to slap a custom block on this and overclock, but it depends on how strong the VRM's are. Similar to the 780/Titan issue of the VRM's being a little less than ideal for 1300+ OC's on the reference cards. Granted it was achievable, but too much power through those puppies and they were liable to pop. Not so sure how a dual chip VRM assembly would deal with the intense TDP, stress and overall heat. It wouldn't surprise me to see a voltage limit on this.